The present invention generally relates to cylinder mechanisms used in firearms, and more particularly to an improved mechanism that permits indexing of cylinders used in so-called “solid frame” revolvers.
Solid frame revolvers basically include a frame, a barrel secured to the front of the frame, a cylinder rotatably mounted in the frame and having a ratchet and a plurality of longitudinal chambers bored through the cylinder from its front end to rear end for receiving cartridges, a trigger pivotably mounted to the frame below the cylinder, and a hammer pivotably mounted to the frame behind the cylinder. Unlike other revolvers which pivot the cylinder assembly either upward or laterally out of the frame to give access to the cylinder chambers for loading or unloading, in solid frame revolvers a loading gate cutout in the rear of the frame provides access to the chambers for loading in cartridges through an openable/closeable loading gate. A cylinder pawl, which may be attached to the hammer, rotates the cylinder when the hammer is cocked or when the trigger is pulled. A cylinder latch is provided for preventing rotation of the cylinder when a cartridge is fired. The cylinder latch is configured to releasably engage a plurality of cylinder latch notches each corresponding to one of the cartridge receiving chambers. The cylinder latch engages each of the notches in succession as the cylinder is rotated.
One early approach used to load or unload cartridges in solid frame single action revolver designs originating in the 1800's is as follows. The hammer is pulled back rearward from its fully forward position to a “half cocked” loading notch position, which lowers the cylinder latch downward into the frame so that the cylinder can be freely rotated in a clockwise direction (when viewed from the vantage point of a user at the rear of the revolver). The loading gate is opened and the cylinder manually rotated counter-clockwise until it stops; the cylinder being reverse indexed in the counter-clockwise direction by the pawl which moves forward and upwards (from its rear and downwards position) when the hammer is “half-cocked” and engages the cylinder ratchet. A chamber is now precisely aligned with the loading gate frame cutout at the reverse index position of the cylinder, and a single cartridge may now be either inserted or removed from that chamber. When finished loading or unloading the desired number of cartridges into the cylinder of the revolver, the loading gate is closed. The hammer may now be moved forward and returned to its fully forward position, or pulled back fully rearward to a “full cocked” position if the revolver is ready to be fired.
Another approach used to load and unload cartridges in a newer solid frame revolver design as described in U.S. Pat. No. 4,307,530 eliminates the “half cocked” loading notch position and enhances convenience when loading or unloading the revolver. This design advantageously allows cartridges to be inserted or removed from cylinder chambers with the hammer in the fully forward “uncocked” position. Opening the loading gate lowers the cylinder latch downwards into the frame so that the cylinder can be freely rotated in a clockwise direction without “half cocking” the hammer. The cylinder is reverse indexed in the counter-clockwise direction by the pawl engaging the cylinder ratchet; however, no chamber is precisely aligned with the loading gate frame cutout when the cylinder stops at each reverse index position to allow a cartridge to be loaded or unloaded from the chamber. This is because the pawl is still in its rear and downwards position, and engages the cylinder ratchet at a different location than in the older single action revolver design discussed above. Additional manual manipulation of the cylinder by the user and time is required to precisely align each cylinder chamber with the loading gate frame cutout by sight. Such manual manipulation may be inconvenient and cumbersome to some users. Thus, there is a need for a solid frame revolver which can be more easily and rapidly loaded or unloaded with the hammer in the fully forward position, without the need to first “half-cock” the hammer.